Diagnosis
The form UIBB with the configuration &V1& is defined for thecontained entity type &V4& of entity typeV2. therefore it cannot be used within entity type v3.
Note: Within one entity type, you can use form UIBBs of another entitytype only if they are not defined for a contained entity type.

Procedure
Remove the form UIBB with configuration &V1& from the UIBBs of entitytype &V3&.